This invention relates to esophageal probes, and more particularly, to an esophageal probe for performing transesophageal atrial and ventricular pacing and electrocardiographic (ECG) recording and monitoring.
Esophageal catheters for performing various functions are well known in the art. These include catheters for cardiac pacing or recording as disclosed, for example, in U.S. Pat. Nos. 4,937,521 and 5,154,387. Another type of catheter is an esophageal stethoscope which includes a diaphragm for listening to heart and breath sounds. Most esophageal stethoscopes also incorporate thermistor sensors for monitoring core body temperature. The thermistor is positioned at the distal end of the esophageal stethoscope, just beyond the distal margin of the acoustic diaphragm. When prior art esophageal stethoscopes are in a position to best discern breath sounds, the thermistor measurement is affected by the movement of relatively cold gases which are inspired during mechanical or artificial respiration. In one prior art esophageal stethoscope, the thermistors are positioned approximately 7 cm distal to the distal margin of the acoustic diaphragm.
Prior art thermistor equipped esophageal stethoscopes capable of ECG recording and/or cardiac pacing generally include bipolar electrodes that are located proximal to the acoustic diaphragm. This configuration has been found to be undesirable because heart sounds are best heard with the electrode center point withdrawn 5 cm, and breath sounds are best heard with the electrode center point 10 cm from the point of minimum pacing thresholds. Thus, the pacing and recording electrodes in prior art esophageal stethoscopes are not correctly positioned relative to the acoustic diaphragm.
Pacing and recording electrodes of prior art esophageal stethoscopes generally comprise a band or ring of conductive material which surrounds the probe. These have been found to be unsatisfactory because they tend to become dislodged, i.e. slip along the tubular barrel assembly thereby exposing bare wire connectors that could damage tissue lining the esophagus. In addition, when band or ring electrodes are used for cardiac pacing they have high current requirements due to current dispersion.